I'm not really into fashion or style so please go easy on me! 
I hate moving stuff between handbags so I tend to buy one and use it until it falls apart, then buy the next one. My last couple of bags were mid to dark grey. I mostly wear black or blue pants and shoes with a variety of colour tops. I've decided that I would like a leather backpack this time, which will hopefully last for years and years, but I can't find one in dark grey. Which of these do you think would work best, or what colour do you think I should look at? I've read that tan is a colour that goes with most things?
Light_Grey
Dark_Brown
(In case you want to suggest something from a specific shop, I'm not in the UK.)